Objective and quantitative evaluation of functions of body tissue is important in diagnosing diseases of the body tissue. For example, in diagnosis of cardiac disease, a quantitative evaluation method has been attempted, in which cardiac wall motion is quantitatively evaluated by using echocardiography.
In recent years, a Cardiac Resynchronization Therapy (CRT) for performing biventricular pacing on a patient with significant heart failure has attracted attention, and it becomes important to quantitatively evaluate cardiac wall motion by using echocardiography in order to determine the application of CRT in advance or to evaluate the effect of the therapy.
CRT is a therapy that can improve cardiac wall motion dyssynchrony, which generally occurs in a patient with significant heart failure, and that provides significant improvement in symptoms in a patient who can benefit from CRT (Responder). On the other hand, it is known that approximately 30 percent of patients with heart failure receive little or no benefit from CRT (Non Responder) as of 2005. “Non Responder” indicates a patient who has heart failure other than the dyssynchrony. Conventionally, the application of CRT is determined on the basis of a QRS duration on an electrocardiogram and a left ventricular Ejection Fraction (EF). For example, a patient with the QRS duration longer than “130 milliseconds” on the electrocardiogram and the left ventricular ejection fraction less than or equal to 35% is determined as a subject to whom CRT is applicable. However, with the above criteria, a patient who has heart failure other than the dyssynchrony may be determined as a subject to whom CRT is applicable, resulting in “Non Responder”.
Therefore, there has been an attempt to extract only the dyssynchrony through a quantitative evaluation method using echocardiography. Examples of the quantitative evaluation method using echocardiography include a method using speckle tracking, in which points set on a myocardium in an ultrasound image are tracked on the basis of a speckle pattern that is specific to the ultrasound image. For example, the heart of a patient is three-dimensionally scanned in a chronological order to collect volume data and the volume data is analyzed by the speckle tracking, so that it becomes possible to three-dimensionally and quantitatively evaluate the wall motion of each of the left ventricle, the right ventricle, the left atrium, and the right atrium.
Meanwhile, factors for determining whether to apply CRT or not include the degree of atrioventricular wall motion synchrony (between the left atrium and the left ventricle) or interventricular wall motion synchrony (between the right ventricle and the left ventricle), in addition to the degree of left ventricular wall motion synchrony. That is, the determination on whether to apply CRT or not depends on the degree of dyssynchrony of these factors.
However, the conventional technology described above is made to separately analyze the functions of the four chambers of a heart, and in particular, to three-dimensionally evaluate the dyssynchrony of the cardiac wall motion in the left ventricle. That is, with the above-described conventional technology, it is impossible to three-dimensionally analyze a difference in the interventricular wall motion synchrony, the interatrial wall motion synchrony, and the atrioventricular wall motion synchrony.